The invention relates to an apparatus for determining the filling quantity of lubricating oils in drive installations.
Such determinations are effected nowadays in the form of a filling level determination, usually manually with the aid of a dipstick. It is furthermore known to determine the filling level automatically with the aid of electrical pickup elements, in particular, which operate capacitively or with the use of a hot-wire element. In this case, determination takes place either during operation or directly at the completion of operation of the drive installation. Both possibilities exhibit the drawback that they yield an entirely inadequate picture of the actually existing amount of lubricating oil. The reason for this is that the lubricating oil is still within the lubricating oil cycle during and at the end of operation, and the filling level normally present in a collecting vessel simulates an oil quantity that is too low. Frequently, the lubricating oil level is, in this case, brought to the seemingly correct, but in reality excessive level by replenishing lubricating oil. The use of a pickup means having only one sensor, in a single hot-wire element, for example, moreover has the disadvantage that no distinction can be made between the condition of having an oil level that is below the desired or minimum filling level due to oil loss, and the condition of having such an oil level due to an inclined positioning of the automotive vehicle.
A feature of the invention is the provision of an apparatus of the type discussed above permitting a reliable indication of the actual lubricating oil quantity.
This is attained by providing that a timing member activates a filling level pickup after a predetermined time of several minutes following the shut-off of the drive installation; that the filling level pickup comprises two sensing elements arranged in proximity to each other, one above the other; and that an output signal for an abnormal filling level is transmitted if the two sensing elements yield differing responses.
The invention is based on the fact that the lubricating oil level reaches its original value only a certain time after end of operation of the drive installation--assuming that no losses have occurred. Only thereafter is the filling level to be determined. A loss of lubricating oil can be recognized in a simple way only at this point in time. An unambiguous indication is achieved by use of the two sensing elements, since, in case of an inclined positioning of the automotive vehicle, both sensing elements are immersed or have emerged, and respond identically.
The invention can be realized in a great variety of ways. Thus, it is possible, for example, to provide that the timing member has a constant switching time. This version is distinguished by special simplicity.
In contrast thereto, improved adaptation to the course of the lubricating oil level is obtained after the end of operation of the drive installation if the predetermined time period is dependent on an operating temperature of the drive installation. This can be, for example, the temperature of the coolant or of the lubricating oil proper. In this way, the factor can be taken into account that lubricating oil exhibits varying viscosity at different temperatures, and the original filling level, assuming no losses have occurred, will be reached at different times. By this adaptation of the switching time of the timing member, it becomes possible to determine the lubricating oil level, independently of the temperature of the lubricating oil, at approximately the instant at which it should have attained the original value. This determination thus takes place relatively frequently precisely in instances of successive short-term operations of the drive installation and offers assurance that a lubricating oil loss can be definitely recognized.
A thus-recognized loss can be compensated for in various ways. On the one hand, with the aid of the filling level pickup signal, an optical indication can be made showing the necessity for replenishing lubricating oil. However, the pickup signal can also be applied to a conventional lubricating oil replenishing device.
By means of such a device, the lubricating oil level can be automatically brought to the required level. The mode of operation of this device can be such that in all cases a definite amount is refilled. In this connection, one of the basic ideas of the invention can be utilized, namely to consider temporal characteristics of the lubricating oil. This characteristic has the consequence that, within the same time period, depending upon the temperature, a different amount of lubricating oil is being replenished. In order always to obtain the same amount of refill, it is thus advantageous to control the time period during which lubricating oil is being replenished in dependence on the temperature. Such replenishment can be effected with the aid of a conventional lubricating oil pump.
The amount being replenished can be dimensioned so small that overfilling is excluded with maxiumum safety. Such a small amount of refill, however, has the result that the required lubricating oil level frequently is not attained with a single refilling step. In this case, refilling is to be performed iteratively. A filling level determination after a preceding refilling step is carried out at regular time intervals until the required lubricating oil level has been reached. These successive filling level determinations are likewise to be executed at a predetermined temporal interval in order to obtain, with relatively little expense, a precise information on the actually present amount of lubricating oil. For this purpose, again, the timing member can be utilized, controlling the successive refilling operations.